Mixing apparatus and method for manufacturing an emulsified fuel

ABSTRACT

A mixing apparatus is disclosed. The mixing apparatus comprises a mixing device having a constant flow area. The mixing device is configured to create a shearing environment. Several types of mixing apparatus are disclosed. Methods for producing aqueous fuel emulsions with consistently uniform dispersed phase particle sizes using a mixing apparatus are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation and claims the prioritybenefit of U.S. patent application Ser. No. 13/929,777 filed Jun. 27,2013, which is a continuation and claims the priority benefit of U.S.patent application Ser. No. 13/487,143 filed Jun. 1, 2012, now U.S. Pat.No. 8,568,019, which is a continuation and claims the priority benefitof U.S. patent application Ser. No. 12/872,669 filed Aug. 31, 2010, nowU.S. Pat. No. 8,192,072, which is a divisional and claims the prioritybenefit of U.S. patent application Ser. No. 11/853,548 filed Sep. 11,2007, which is a divisional and claims the priority benefit of U.S.patent application Ser. No. 10/754,885 filed Jan. 9, 2004, theentireties of the aforementioned applications which are incorporated byreference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a mixing device for manufacturing anaqueous fuel, and more particularly to a specially designed mixingdevice that creates a superior aqueous fuel emulsion from a hydrocarbonfuel, water, and an aqueous fuel emulsifier package.

Recent fuel developments have resulted in a number of aqueous fuelemulsions comprised essentially of a carbon-based fuel, water, andvarious additives, such as lubricants, emulsifiers, surfactants,corrosion inhibitors, cetane improvers, and the like. These aqueous fuelemulsions may play a key role in finding a cost-effective way forinternal combustion engines including, but not limited to, compressionignition engines (i.e., diesel engines) to achieve the reduction inemissions below the mandated levels without significant modifications tothe engines, fuel systems, or existing fuel delivery infrastructure.

Advantageously, aqueous fuel emulsions tend to reduce or inhibit theformation of nitrogen oxides (NOx) and particulates (i.e., combinationof soot and hydrocarbons) by altering the way the fuel is burned in theengine. Specifically, the fuel emulsions are burned at lowertemperatures than conventional fuels due to the presence of water. This,coupled with the realization that at higher peak combustion temperaturesmore NOx are typically produced in the engine exhaust, one can readilyunderstand the advantage of using aqueous fuel emulsions.

As is well known in the art, the constituent parts of such aqueous fuelemulsions have a tendency to separate or be unstable over time becauseof the different densities or relative weights of the primarycomponents, as well as other factors including the immiscibility of thecompounds. As an example, middle distillate hydrocarbon sources have adensity of about 0.85 while water sources have a density of about 1.0.Because the gravitational driving force for phase separation is moreprominent for larger droplets of water, emulsions containing relativelysmaller droplets of water will remain stable for longer periods of time.Aqueous fuel emulsion breakdown or phase separation is also influencedby how quickly the water droplets coalescence, or flocculate. Theemulsion breakdown is also influenced by the environment in which theaqueous fuel is subjected. Any breakdown in the aqueous fuel emulsioncan be extremely damaging if not detected before use in combustion.Given the microscopic nature of the suspended particles with thediscontinuous phase, aqueous fuel emulsions can look acceptable to thenaked eye but can actually be considered unacceptable when subjected toquality control standards to one skilled in the art.

Determining the amount of the emulsifier necessary for creating aspecific emulsion of a water source and a hydrocarbon source cangenerally be calculated with calculations common to the art based onmaterial densities, particle sizes of the discontinuous phase, etc. Suchmeasurements are typically summarized in a particle distribution curveof the discontinuous phase.

It is commonly recognized that aqueous fuel emulsions can be produced bymixing a liquid hydrocarbon source, an emulsifier source, and a watersource. The art of making aqueous fuel emulsions basically relates tothree aspects:

-   -   1) The specific chemistries of the aqueous fuel emulsifier;    -   2) The specific sequences in which each of the ingredients (or        portions thereof) are mixed with the other ingredients (or        portions thereof); and    -   3) The specific mechanical mixing procedures of the ingredients.

Chemistries for emulsifiers are generally composed of surfactants orsoaps, among other things, that comprise a mixture of at least twocomponents: one that is predominantly hydrocarbon soluble and the otherthat is predominantly water soluble so that the surfactant is balancedsuch that the interfacial tension between the hydrocarbon and waterphases is substantially zero. In other words, each of these chemistriesplays a critical role in breaking down the surface tension between theoil and water so a bond can form between the different molecules and tohelp disperse the water particles (from attracting to each other in thecase of an oil phase). This is basically completed through threedifferent types of electrical charged chemistries referred to ascationic (positive charge), anionic (negative charge) and non-ionic(neutral charge), or combinations thereof.

In many cases the emulsifier packages are designed to be soluble in thediscontinuous phase. The amount of the emulsifier as a percent of theaqueous emulsified fuel will vary based on several factors which includethe type and amount of continuous and discontinuous phase, the chemicalcomposition of the emulsifier, and the particle sizes of thediscontinuous phase.

While a range of different sequences have been recognized, it isgenerally understood that the principles of aqueous fuel emulsionsdictate that the emulsifier supply should be mixed with the externalphase of the aqueous fuel emulsion first (or portions thereof) and thenwith the discontinuous phase (or portions thereof) second.

For example, in the case of an oil-phased emulsion, the emulsifiersupply would be first mixed with the hydrocarbon source before it ismixed with the discontinuous phase of water. Conversely, in awater-phased emulsion the emulsifier supply would be first mixed withthe water source (or portions thereof) before it is mixed with thediscontinuous phase of hydrocarbon fuel (or portions thereof). In thecase where portions are premixed, the balance is introduced at asubsequent point as the aqueous fuel emulsion is manufactured.

While there can be several mixing stations during the emulsificationprocess, a high-shear mixing stage is usually required when a watersource is mixed with a hydrocarbon fuel source. Prior to the high-shearmixing, the various stages can be mixed with less intense mixingdevices, such as in-line mixers or other common liquid agitators,because the chemicals being mixed have relatively compatible chemicalproperties. Because of the very different chemical properties of waterand oil, significant amounts of mechanical energy are required to reducethe discontinuous phase to sizes where they can contribute to a stableaqueous fuel emulsion.

To date, high-shear mixers such as commercially available rotor-statorunits and ultrasonic devices have been commonly referenced despite thefact that they were designed and sold primarily for the emulsificationof non petroleum-related products such as foods products, cosmeticproducts and chemical products.

Several related art references have disclosed specific high sheardevices for producing or blending a fuel emulsion. For example, U.S.Pat. No. 6,383,237 to Langer discloses the use of a rotor-stator mixer,when the hydrocarbon and water source are mixed, as does U.S. Pat. No.5,873,916 to Cemenska. In both patents, the use of the commerciallyavailable high shear devices from well-recognized companies in the fluidagitation industry as part of their multi-step and multi-sequence fuelemulsion blending systems is disclosed.

Rotor stators basically provide shearing by a combination of a spinningblade, flow forced through a screen and/or a combination of both.Because the particle size of the discontinuous phase is largelydetermined by the shear rate of the high shear mixer, it is common forthe discontinuous phase to have a wide range of particle sizes as agiven portion is cut with the blade, a different portion is forcedthrough a screen and another portion is subjected to both. To compensatefor this occurrence many high shear mixers include dual or multiplestaged rotor mixers or looped circuits, which allow aqueous fuelingredients to be subjected to additional shear thereby increasing thepopulation of uniform dispersed phase particle sizes. However, theseadditional high shear mixing devices or looped systems are moreexpensive and less efficient in terms of volume output, and aredifficult to control correctly.

Despite the widespread use of high shear mixers in the aqueous fuelemulsion industry as well as other participants in the fluid agitationindustry, there is almost no fundamental basis by which to theoreticallypredict or experimentally assess their performance. This fundamental isbetter illustrated through a general review of the shear rate and itscalculation.

Shear is a force that is applied parallel to a surface, as illustratedin FIG. 1.

The forces are opposite as the square has to be in static equilibrium.This shear tends to elongate a solid, and in a liquid tends to createturbulence and eddies.

The shear formula that has been used for analysis of the physicalprocesses in making emulsified fuels is as follows in FIG. 2 andEquation 1:

$\begin{matrix}{{{Shear}\mspace{14mu} {force}} = \frac{VAu}{Bgc}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Where: V is the velocity of the moving plate

-   -   A is the area of the plate    -   u is the viscosity of the fluid in question    -   gc is the gravitational constant, 32.2 ft/sec    -   B is the separation distance between plates.

This equation was developed and is commonly used to determine theviscosity of liquids by measuring the force created by rotating a platein the fluid of question. It is also directly applicable to anysituation where one plate is moving in relation to another, such as in acolloid mill.

For flow between two surfaces, the physical situation is as follows inFIG. 3 and Equation 2:

$\begin{matrix}{{{Shear}\mspace{14mu} {force}} = \frac{2\; {VAu}}{Bgc}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

Where: V is the velocity of the moving plate

-   -   A is the area of the plate    -   u is the viscosity of the fluid in question    -   gc is the gravitational constant, 32.2 ft/sec    -   B is the separation distance between plates.

Although the linear velocity profile is an approximation (it is knownthat the velocity profile is parabolic in nature) it does provide amethod for comparative calculation. As shear is present on both plates,the total shear force exerted on the fluid is about two times that fromEquation 1.

One needs to recognize the fact that these calculations are not precise,as there are assumptions in their creation and in their application.However, these calculations illustrate the basic forces in fluid shearand can be used to develop relative force values for different shearmodes.

Due to the rather imprecise methods available to calculate shear incommercially available unit scale-up and operation of these high-shearunits as a component of a blending process of the aqueous fuel emulsionsis generally completed by trial and error. Consequently, many of thecommercial blending units available for blending aqueous fuel emulsionsare configured around the limitations of the commercially available highshear units. This is one of the reasons the commercial aqueous fuelemulsion blending units require recirculation capabilities ormulti-staged shearing (despite their higher costs or impact on lowercapacity) to enable the water particles to be reduced to the desiredparticle size.

Because of problems inherent with the commercially available high shearmixing units such as the rotor stator, the effectiveness of the shearmixing units can only be varied by controlling the rate and frequency inwhich the emulsion material is subjected to high shear mixing. As statedabove, the commercially available units may not be capable of creating aconsistently uniform family of particle sizes of the discontinuous phasein the most practical and cost effective manner. This can create afairly wide distribution curve for a family of particle sizes of waterand in most cases creates a bi-modal curve. Having a consistentdiscontinuous phase particle size is not only important to create thefoundation for a stable emulsion but it is critical in determining therequired amount of emulsifier that is required. Consequently, it wouldbe desirous to have a mixing system that creates a more uniformpopulation of particle sizes of the discontinuous phase. A narrowerparticle distribution curve thereby creates an even distribution of theemulsifier sources between hydrocarbon source and the water source.

SUMMARY OF THE CLAIMED INVENTION

The present invention addresses the aforementioned problems byincorporating a specially designed mixing unit into a blending systemand method for producing aqueous fuel emulsions with consistentlyuniform dispersed phase particle sizes with a relatively inexpensivemixing device. Specifically, the present invention relates to aspecially designed mixing device that creates an aqueous fuel emulsionfrom a source of hydrocarbon fuel, a source of water, and a source ofsaid aqueous fuel emulsifier package by incorporating a small area highvelocity-mixing device that produces the appropriate mixing environmentfor the individual compounds to make an aqueous fuel with relativelyhomogenous particle sizes of the discontinuous phase.

A mixing apparatus is disclosed. The mixing apparatus comprises a mixingdevice having a constant flow area. The mixing device is configured tocreate a shearing environment.

Another mixing apparatus is disclosed. The mixing apparatus comprises afluid shear generator body having a first cavity with an inlet having apredetermined flow area and a second cavity with an outlet having apredetermined flow area. The first cavity has an inlet configured toreceive liquids and the second cavity has an outlet configured to couplethe liquids mixed in the fluid shear generator body. The mixingapparatus also comprises a shear cone disposed between the first cavityand the second cavity. The mixing apparatus also comprises a shear coneseat disposed between the first cavity and the second cavity. The shearcone seat matingly receives the shear cone and the shear cone seat isparallel to an upper surface of the shear cone. The mixing apparatusalso comprises a control stem integral with the shear cone. The controlstem is configured to adjust the shear cone. The control stem isconfigured to control a gap between the shear cone and a shear cone seatwith the gap having a predetermined flow area.

Another mixing apparatus is disclosed. The mixing apparatus comprises adisc body having a first face and a second face opposite the first face.The disc body has a disc wall disposed between the first face and thesecond face. The mixing apparatus also comprises at least one flowpassage extending through the disc body from the first face to thesecond face. The at least one flow passage has a constant flow area. Thedisc body is configured to shear a fluid flowing through the at leastone flow passage.

A method of producing aqueous fuel emulsions with consistently uniformdispersed phase particle sizes using a mixing apparatus is disclosed.The method comprises disposing aqueous fuel emulsion producing liquidsinto a mixing device. The mixing device can be either mixing apparatusas discussed above. The method also comprises flowing the aqueous fuelemulsion-producing liquids through a constant flow area of the mixingdevice.

BRIEF DESCRIPTION OF THE FIGURES

Referring now to the figures, wherein like elements are numbered alike:

FIG. 1 is a prior art figure illustrating shear force.

FIG. 2 is a prior art figure illustrating the shear formula used foranalysis of the physical processes in making emulsified fuels between amoving surface and a stationary surface;

FIG. 3 is a prior art figure illustrating the shear formula used foranalysis of the physical processes in making emulsified fuels betweentwo stationary surfaces;

FIG. 4 is a schematic representation of an exemplary manufacturingsystem for an aqueous fuel emulsion;

FIG. 5 is a cross section of an exemplary mixing device;

FIG. 6 is a frontal view of another exemplary mixing device; and

FIG. 7 is a side view of the exemplary mixing device of FIG. 6.

DETAILED DESCRIPTION

Those of ordinary skill in the art will realize that the followingdescription is illustrative only and not in any way limiting. Otherembodiments will readily suggest themselves to such skilled persons.

FIG. 4 illustrates a schematic representation of a manufacturing system10 for an emulsion. In the preferred embodiment, the manufacturingsystem operates at ambient conditions. The manufacturing system 10comprises a series of inlets for the raw materials. For illustrationpurposes, inlet 12 provides a hydrocarbon fuel inlet 14 provides anemulsifier package, and inlet 16 provides a source of water and can beconnected to the specially designed mixing device 32 at an appropriateplace.

Inlets 12 and 14 provide a hydrocarbon fuel and an emulsifier package,respectively, to a fuel pump 18 disposed at the intersection of inlets12 and 14 with lead 24. The fuel pump 18 transfers the hydrocarbon fueland the emulsifier package to a mixing station pump 22 at a selectedflow rate. The hydrocarbon and emulsifier package would flow at a rateof about 0.87 gallons per minute (gpm) in an emulsifying system with acapacity of about 1 gpm. A flow measurement device 30 is adapted tocontrol the flow of the hydrocarbon fuel and emulsifier package mixturedirected from the mixing station pump 22 to the mixing device 32.

Inlet 16 provides a source of water to a water pump 20 through lead 26.The water pump 20 directs the source of water through a flow measurementdevice 28. The flow of water is then transferred to the speciallydesigned mixing device 32 at a selected flow rate. The water would flowat a rate of about 0.13 gpm in an emulsifying system with a capacity ofabout 1 gpm.

After flowing through the flow measurement devices, leads 24 and 26direct the materials to the specially designed mixing device 32. Thematerials may be transferred using existing pumps (as illustrated),using additional pumps (not shown), by gravity, or by other methodsknown in the art.

Following creation of the emulsion, the emulsion can be used immediatelyafter manufacture or directed through a lead 34 to a holding tank 36 forfuture use.

The above-described blending system is particularly suited for preparinga water blend fuel or aqueous fuel emulsion. Specifically, fuels such ashydrocarbon petroleum fuels, blends of hydrocarbon petroleum fuels,blends of hydrocarbon fuels with derivatives of bio mass, derivatives ofbio-mass, and other forms of calorific bearing liquids. The preferredvolumetric ratio of calorific bearing liquid to water is about 50% toabout 99% of the total volume of the aqueous fuel emulsion. Thevolumetric ratio of additives is less than about 1% to about 5% of thetotal volume of the hydrocarbon fuel. The fuel emulsion additives usedin the above description can be the following ingredients (orcombinations thereof) including surfactants, emulsifiers, detergents,de-foamers, lubricants, corrosion inhibitors, anti-freeze inhibitorssuch as alcohol, and the like.

A mixing device is disclosed. The mixing device relies on a shearingenvironment where the amount of mixing energy as defined by Equation 2is about equal at the beginning, middle and end of the mixing geometry.By extending the amount of area in contact with the ingredients, theprocess has effectively increased the shear force by increasing thevariable A in Equation 2. With no moving parts this consistent mixingrate is ensured so long as the flow rates are maintained constant. Inthis example, the velocity profile, the distance between the twostationary plates, was designed based on the particular flow rate of thesystem illustrated in FIG. 3. It is understood that the velocity profileor shear forces could easily be increased or decreased based on thedesired volume output of the aqueous fuel blending system. Similarly,the shear forces could be changed by using any of a range of differentenvironments which provide a consistent environment for mixing such asnarrowing the space between the two surfaces or bending the path offlow.

A method for manufacturing an aqueous fuel emulsion is also disclosed.The method comprises blending a flow of a liquid hydrocarbon fuel with aflow of an emulsifier package and a flow of water to form a firstmixture. Next, the method comprises directing the first mixture into amixing vessel and mixing the first mixture to form the aqueous fuelemulsion. The mixing vessel incorporates the specially designed mixingdevice, which relies on a shearing environment where the amount ofmixing energy as defined in the shear rate is about equal at thebeginning, middle and end of the mixing process.

FIG. 5 illustrates a schematic representation of an exemplary mixingdevice 32. In the preferred embodiment, the mixing device 32 is aplastic or metal device. The mixing device 32 is preferably a metalmaterial that is non-corrosive to the liquids encountered when utilizingthe mixing device 32. The mixing device 32 preferably operates atambient conditions.

With reference to FIG. 5, the mixing device 32 is composed structurallyof a fluid shear generator body 38 having two cavities 40, 42 that areopen for the transfer of liquids through the fluid shear generator body38. The fluid shear generator body 38 has an inlet 44 in a first cavity40 for the liquids to be passed into the fluid shear generator body 38.The liquids pass through the first cavity 40 to the second cavity 42through a shear cone 46 and shear cone seat 48. The liquids are mixedand passed through an outlet 50 of the second cavity 42 to the end useor storage (not shown).

Within the center of the fluid shear generator body 38 between the firstcavity 40 and the second cavity 42, is the shear cone 46. The shear cone46 is adjusted by the control stem 52 to control the distance (or gap)54 between the shear cone 46 and the shear cone seat 48.

The shear cone 46 and the shear cone seat 48 are designed such that thegap 54, the distance between the shear cone 46 and the shear cone seat48 are equal to the gap 56. The height of the gap 54 may be varied byadjusting the shear cone 46 with the control stem 50 by means of aset-screw in a manual mechanism, and the like, or in more automatedversions with a hydraulic or pneumatic pump (not shown), and the like.

The size of the shear cone 46, the shear seat 48, and the gap 54 isdependent upon the flow rate of the liquids to be processed in the fluidshear generator body 38. For example, at a flow rate of about 1 gallonper minute (gpm), the shear cone 46 is about 0.15 inches in height witha diameter of about 0.23 inches to about 0.31 inches. The shear cone 46is sized such that when the control stem 52 is adjusted to set the shearcone 46 in the shear cone seat 48 so that the shear cone 46 iscompletely flush with the upper surface 58 of the shear cone seat 48.The shear cone seat 48 is always parallel to the shear cone surface 60.

FIGS. 6 and 7 illustrate a schematic representation of another exemplarymixing device 32. In the preferred embodiment, the mixing device 32 is aplastic or metal device. The mixing device 32 is preferably a metalmaterial that is non-corrosive to the liquids encountered when utilizingthe mixing device 32. The mixing device 32 preferably operates atambient conditions.

The mixing device 32 illustrated in FIGS. 6 and 7 is composedstructurally of a disc body 62 having a first face 64 and a second face66. Between the first face 64 and the second face 66 is a disc wall 68.The disc body 62 has several flow passages 70 extending through the discbody 62 from the first face 64 to the second face 66. The flow passages70 have a constant flow area.

The size of the disc body 62 and flow passages 70, and the number offlow passages is dependent upon the flow rate of the liquids to beprocessed in the disc body 62. For example, at a flow rate of 10 gpm,the disc body 62 can have 110 flow passages 70 having a diameter ofabout 0.03 inches. The disc body 62 can be about 1 inch thick. The sizeof the disc body 62 can be extended by making the disc body 62 thickeror by utilizing several disc bodies stacked upon one another.

Referring to FIGS. 5 and 6, the mixing device 32 relies on a shearingenvironment where the amount of mixing energy as defined in the shearrate is about equal at the beginning (gap 54), middle and end (or thegap 56) of the mixing process. By extending the length of time theingredients are exposed to a consistent mixing environment, the processhas effectively increased the shear force by increasing the variable Vin Equation 2. With no moving parts, this consistent mixing rate isensured so long as the flow rates are maintained constant. In FIG. 3,the velocity profile, the distance between the two stationary plates,was designed based on the particular flow rate of the system illustratedin FIG. 5.

It is understood that the velocity profile or shear forces could easilybe increased or decreased based on the desired volume output of theaqueous fuel blending system. Similarly, the shear forces could bechanged by using any of a range of different environments that provide aconsistent environment for mixing. For example, multiple tunnels couldbe introduced rather than a single tunnel. This could increase thecapacity as well as the amount of mixing depending on various factorswell known to those in the art. Alternatively, the straight tunnelscould be bent or curved in a variety of ways to enhance the mixingenergy.

The above-described apparatus can be used to create an aqueous fuelemulsions with consistently uniform dispersed phase particle sizes.Aqueous fuel emulsion producing liquids are disposed into a mixingdevice. Any of the mixing devices as discussed above can be utilized.The aqueous fuel emulsion-producing liquids are transported through aconstant flow area of the mixing device. The flowing of the liquidsthrough the mixing devices creates an aqueous fuel emulsion havingconsistently uniform dispersed phase particle sizes.

EXAMPLE 1

In this example, the Rotor Stator Mixer used is a Silverson™ model 150 Lwith a fine mesh screen (having a hole size of about 0.02″) powered by a60 HZ motor at about 100%. The individual ingredients and aqueous fuelemulsion were subjected to recirculation within the rotor stator mixingfive times. At the end of each pass, a sample was taken for measurement.

The mixer used is illustrated in FIG. 5. The individual ingredients andaqueous fuel emulsion was moved at a rate of 1 gpm and the height of thegap was about 0.03 in. The individual ingredients of the aqueous fuelemulsion were subjected to the specifically designed mixer mixing onetime. A sample from the first pass was taken for measurement.

The aqueous fuel emulsion was prepared under the general methoddescribed previously with the constituents also described. The particlesizes of the discontinuous phase (or the water) were measured by anaccoustizer. Referring to Tables 1 and 2, the accoustizer providedmeasurements of the water particles suspended for four data points. Thefirst data point is D10, which quantifies the percentage of particlesunder a given micron size relative to the entire population ofdiscontinued particles. For example, 10% of the particles measured willbe less than the D10 reading while 90% will be larger than the D10reading. The second data point is D50 which quantifies the percentage ofparticles under a given micron size relative to the entire population ofdiscontinued particles. The third data point is D90, which quantifiesthe percentage of particles under a given micron size relative to theentire population of discontinued particles. The fourth data point isthe mean of all the data points, which is the average size of allparticles measured.

TABLE 1 Rotor Stator Mixer d10 d50 d90 mean Pass 1 0.1713 0.8743 4.46362.075 Pass 2 0.1240 0.6211 3.1102 1.445 Pass 3 0.1523 0.7500 3.69371.716 Pass 4 0.1593 0.7200 3.2548 1.514 Pass 5 0.1509 0.7015 3.25991.515

TABLE 2 Present Invention Mixer d10 d50 d90 mean Pass 1 0.1223 0.49351.9920 0.934

The objective of this example is to match the two mixing devices with anequal amount of energy and shearing as best as could be determined usingthe previously described formula in Equation 2.

The aqueous fuel emulsion product made by the specifically designedmixing device had a mean size that was generally smaller when comparedto the rotor stator shear mixing device with other variables such asflow rate and temperature being constant. In addition, the specificallydesigned mixer demonstrated that a single pass is generally sufficientto achieve particle sizes that are smaller when compared to multiplepasses of the other mixing devices. It is believed although notconfirmed that this relates to the extended time in which the liquid issubjected to mixing in the chamber.

The specifically designed mixing device involves less processing timeand less energy. Furthermore, the specifically designed mixing devicecreates a more narrow population of particle sizes, which will allow fora more efficient distribution of the emulsifier package, as well as amore stable aqueous fuel emulsion.

Rotor stators basically provide shearing by a combination of a spinningblade, force through a screen and/or a combination of both. Because theparticle size of the discontinuous phase is largely determined by theshear rate of the high shear mixer, it is common for the discontinuousphase to have a wide range of particle sizes. Some of the particles arecut with the blade, some of the particles are forced through a screenand some of the particles are a combination. This is demonstrated inTable 1, which illustrates the three different shearing environments towhich the water source, the emulsifying package and liquid hydrocarbonsolutions are subjected. Additionally, it is believed although notconfirmed, that the larger variance in the particle distribution curveas noted above supports this notion. In fact, as the emulsified fuel isre-circulated through the rotor stator the population of largerparticles generally becomes smaller with each pass while the populationof smaller particles remains relatively unchanged. Consequently, itappears that the recirculation is reducing the larger population ofparticles disproportionately to the populations of smaller particles. Byway of example, the smallest population of particles (or D10) decreasedby only about 12% while the medium population (or D50) decreased byabout 20% and the largest population decreased by about 27%.

To compensate for this occurrence many high shear mixers include dualand multiple-staged rotor mixers or looped circuits, which allowemulsion ingredients to be subjected to additional shear therebyincreasing the population of uniform water particle sizes. This wasproven in Example 1 because after one pass about 90% of the particleswere about 4.5 microns or less but after five passes about 90% of theparticles were about 3.25 microns or less. However, these additionalhigh shear mixing devices or looped systems are more expensive and lessefficient in terms of volume output and overall effectiveness inreducing the particle size of the discontinuous phase.

The mixing apparatus of the present invention is less expensive tomanufacture and operate. The simplicity of the operation of the mixingapparatus is desirable because there are no moving parts that can resultin costly failures of the apparatus. The resulting emulsion is a morecost-effective and stable fuel.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings without departing from the essential scopethereof. Therefore, it is intended that the invention not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this invention, but that the invention will include allembodiments falling within the scope of the appended claims.

What is claimed:
 1. A method for producing aqueous fuel emulsions withconsistently uniform dispersed phase particle sizes, the methodcomprising: receiving a flow of a mixture of aqueous fuelemulsion-producing liquids in a mixing device comprising a fluid sheargenerator body having a shear cone and shear cone seat disposed betweena first cavity of the body and a second cavity of the body, wherein theshear cone and shear cone seat are separated by a gap, the gap having aheight and presenting a predetermined flow area; and controlling, with aflow measurement device, a flow rate of the flow from one or more inletsto the mixing device, wherein the mixture of aqueous fuelemulsion-producing liquids through the body is provided at a constantflow rate, and wherein the constant flow rate is selected in relation tothe height of the gap, to generate within the body a shear force on themixture of aqueous fuel emulsion-producing liquids sufficient toemulsify the mixture of aqueous fuel emulsion-producing liquids.